Spinal stenosis is a medical condition in which the spinal canal narrows and compresses the spinal cord and nerves. This is usually due to the natural process of spinal degeneration that occurs with aging. It can also sometimes be caused by spinal disc herniation, osteoporosis or a tumor. Spinal canal is a column, and loss of height equals loss of volume. As a result, canal becomes tight and narrowed.
Spinal stenosis typically affects the lumbar vertebrae, the largest segments of the movable part of the vertebral column, characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body (the lumbar vertebrae are designated L1 to L5, starting at the top). Lumbar spinal stenosis may result in Neurogenic claudication causing pain and/or weakness in the legs, buttocks, or thighs, and/or feet. Neurogenic claudication may also result in loss of bladder and/or bowel control.
The pathophysiology of Neurogenic claudication is thought to be ischemia of the lumbosacral nerve roots secondary to compression from surrounding structures, hypertrophied facets, ligamentum flavum, bone spurs, scar tissue, and bulging or herniated discs. Typically, pain occurs with standing because as you axially load the spine it compresses losing height (and volume) and pinches nerves. Commonly, there is little or no pain when sitting because the spine is unloaded and flexed increasing length (and volume) making more room for nerves.
Currently, patients suffering from severe spinal stenosis have few surgical options to alleviate symptoms including a Laminectomy, a Foraminotomy, and surgical placement of an implant device within the spinous processes. One option is a Laminectomy wherein a portion of the vertebral bone called the lamina is surgically removed. There are many variations of Laminectomy, in the most minimal form small skin incisions are made, back muscles are pushed aside rather than cut, and the parts of the vertebra adjacent to the lamina are left intact. The traditional form of Laminectomy (conventional Laminectomy) excises much more than just the lamina, the entire posterior backbone is removed, along with overlying ligaments and muscles. The usual recovery period is very different depending on which type of Laminectomy has been performed: days in the minimal procedure, and weeks to months with conventional open surgery.
Conventional open Laminectomy often involves excision of the posterior spinal ligament, and some or all of the spinous process, and facet joint. Removal of these structures, in the open technique, requires cutting the many muscles of the back which attach to them. Laminectomy performed as a minimal spinal surgery procedure, however, allows the bellies of muscles to be pushed aside instead of transected, and generally involves less bone removal than the open procedure. The actual bone removal may be carried out with a variety of surgical tools, including drills, rongeurs, and lasers.
Removal of substantial amounts of bone and tissue may require additional procedures to stabilize the spine, such as fusion procedures, and spinal fusion generally requires a much longer recovery period than simple Laminectomy.
In hopes of finding a less invasive procedure to alleviate pain caused by spinal stenosis, physicians have turned to Inter-Spinous Process Decompression, IPD, in which an implant is placed/implanted between the spinous processes of the symptomatic disc levels. These devices are designed to limit pathologic extension of the spinal segments and maintain them in a neutral or slightly flexed position, which may allow patients to resume their normal posture rather than flex the entire spine to gain symptom relief.
Unfortunately, implantation of many of these IPD devices still results in significant trauma to the patient, requiring open incisions and retraction of muscle and tissue. For example, the X-Stop implant, developed by Saint Francis Medical Technologies, L.L.C. covered by a litany of patent applications and issued United States Patents (e.g. U.S. Pat. No. 5,836,948), herein incorporated by reference, requires that the physician make an invasive incision and wedge the implant between the spinous process to push them apart (permanently increasing the spinal column volume).
Thus, integrated IPD devices, methods, and systems allowing for a minimally invasive, percutaneous implantation are needed and are provided herein.